rn-38: Fix version number and URL for Gerrit release 2.15.1

- The link text was 2.5.1 instead of 2.15.1 - The URL pointed to the old /releases/version.md location which was replaced by an html file at the root when the project site was migrated to a new host. It also omitted the anchor to the specific release. Change-Id: I54004441751131d0259905ec3cafaae84a8145d6 Signed-off-by: David Pursehouse <[email protected]>

Author: dpursehouse

_posts/2018-04-18-edition-38.markdown

@@ -308,7 +308,7 @@ Kaartic's patch series will probably also be merged there, too.
 [3.5.1](https://support.gitkraken.com/release-notes/current#v3-5-1)
 * libgit2 [0.27.0-rc3](https://github.com/libgit2/libgit2/releases/tag/v0.27.0-rc3) and
 [0.27.0](https://github.com/libgit2/libgit2/releases/tag/v0.27.0)
-* Gerrit Code Review [2.5.1](https://www.gerritcodereview.com/releases/2.15.md)
+* Gerrit Code Review [2.15.1](https://www.gerritcodereview.com/2.15.html#2151)
 
 ## Other News